Liquefied light hydrocarbon fuel system for hybrid vehicle and methods thereto

ABSTRACT

A liquefied light hydrocarbon (LLH) fuel system for a hybrid vehicle is disclosed. The fuel system comprises an insulated fuel tank having a buffer space, a fuel control valve, wherein an outlet to the fuel tank connects to a first end of the fuel line, wherein an inlet of the fuel control valve connects to a second end of the fuel line and wherein an outlet of the fuel control valve is adapted to connect to a fuel inlet to an internal combustion engine; and a tank heating system comprising: a heating element, wherein the heating element is disposed adjacent to or within the fuel tank; a heating power control system, wherein the heating power control system controls the amount of heat produced by the heating element to vaporize the LLH fuel. Methods of using the fuel system are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent Ser. No.14/052,267, filed on Oct. 11, 2013, which claims priority to U.S.Provisional Patent Application Ser. No. 61/713,587, filed on Oct. 14,2012, for “Liquefied Light Hydrocarbon Fuel System for Hybrid Vehicle.”

TECHNICAL FIELD

The present invention relates to a liquefied light hydrocarbon (LLH)fuel system for a hybrid vehicle and methods thereto.

BACKGROUND OF THE INVENTION

Light hydrocarbons (e.g., natural gas) are abundant in North America. In2010, the U.S. Energy Information Administration (EIA) estimated theU.S. light hydrocarbon reserves to be about 317 trillion cubic feet.Recent developments in light hydrocarbon production have made lighthydrocarbons more economical as an energy source than other petroleumoil products (e.g., gasoline, diesel fuel). Moreover, light hydrocarbonsare environmentally cleaner than other petroleum fuels because lighthydrocarbons produce fewer greenhouse gases (e.g., carbon dioxide,methane).

For use as a fuel, light hydrocarbons may be cooled below their boilingpoint temperature to form liquefied light hydrocarbons (LLH). Forexample, the boiling point of non-compressed methane is about −164° C.or −263° F. at atmospheric pressure. Prior art attempts to deal withvarious challenges related to using a LLH fuel for vehicles powered byan internal combustion engine, such as the following: 1) insulating theLLH fuel from ambient heat; 2) vaporizing the LLH fuel before it entersa combustion chamber of the internal combustion engine; 3) providingenough LLH fuel to the internal combustion engine for sudden surges indemand for power (e.g., acceleration, high speeds, heavy loads); 4)avoiding excessive pressure-build-up inside the fuel tank fromevaporation of the LLH fuel; and 5) minimizing emissions of greenhousegases, especially vapor LLH fuel into the atmosphere when the vehicle isidle.

U.S. Pat. No. 5,373,700 describes a system for storing liquefied naturalgas (LNG) and delivering vaporized LNG to an internal combustion engine.The system comprises an LNG fuel tank, a plurality of heat exchangersand gas regulator valves to maintain and control pressure inside the LNGfuel tank.

U.S. Pat. No. 5,884,488 describes a high-pressure LNG fuel systemcomprising an LNG fuel tank with a plurality of chambers, a cryogenicpump and an engine coolant-heated vaporizer to deliver vaporized LNGfuel to an internal combustion engine at about 3000 psig.

U.S. Pat. No. 6,698,211 describes a high-pressure LNG fuel systemcomprising a fuel tank, a pump and a vaporizer to deliver vaporized LNGfuel to the engine injectors at about 500 to about 3000 psig.

U.S. Pat. No. 6,058,713 describes a high-pressure LNG fuel systemcomprising a high-pressure fuel tank and a vaporizer using ahigh-pressure fuel tank to store the LNG at about 150 psi to about 1100psi and to deliver the vaporized LNG fuel to the engine injectors at anadequate pressure.

The fuel systems described above tend to be complex, heavy, anddifficult to maintain and require specialized components and materialsto withstand cryogenic temperatures (e.g., cryogenic pumps, regulatorvalves, evaporators).

Thus, a LLH fuel system and method is needed that would be simple,light-weight, easy to maintain and utilize predominately standardcomponents and materials.

SUMMARY OF THE INVENTION

The present invention relates to a LLH fuel system for a hybrid vehicleand methods thereto. The novel LLH fuel system addresses the challengesrelated to using a LLH fuel for vehicles powered by an internalcombustion engine.

The first challenge involves insulating the LLH fuel from ambient heat.In other words, the LLH fuel must be maintained at a low temperature tominimize evaporation in a fuel tank. In general, Dewar-type fuel tankswith a double wall and a vacuum chamber between the two walls arerequired to maintain the low temperature as seen in the prior art. Thepresent invention allows the use of a tank with a single wall covered byinsulation and a radiant barrier. Although this may result in moreambient heat leakage into the tank, this incremental heat may be offsetby a mechanism to extract heat from the tank and by theelectronically-controlled extraction of vaporized fuel for consumptionby an internal combustion engine.

The second challenge involves vaporizing the LLH fuel before deliveringthe vaporized LLH fuel to the combustion chamber of the engine. In theprior art, fuel extracted from the tank is vaporized by use of heatexchangers. The present invention uses ambient heat leakage to vaporizethe fuel and supplements the ambient heat by a heating element tovaporize additional fuel as needed.

The third challenge involves providing enough LLH fuel to an internalcombustion engine for sudden surges in demand for power (e.g.,acceleration, high speed and heavy load). The prior art addresses thisissue by use of a cryogenic pump to increase the flow of liquid or vaporfuel to the internal combustion engine. The present inventionaccommodates sudden surges in power by allowing a buffer space in theLLH fuel tank or a buffer tank to provide room for vaporized LLH fuel toaccumulate at sufficient pressure to provide enough LLH fuel to theinternal combustion engine. Further, the hybrid vehicle could beconfigured to limit the range of operation for the internal combustionengine and to draw upon a battery to provide additional energy requiredfor sudden acceleration, high speed and/or heavy loads.

The fourth challenge involves avoiding excessive pressure build-upinside the fuel tank from evaporation of the LLH fuel. Prior artgenerally addresses this issue by venting excess vaporized fuel into theatmosphere. In the present invention, the pressure may be maintained bysizing the buffer space in the LLH fuel tank or the buffer tank to belarge enough to permit vaporized LLH fuel to accumulate and to be drawnwithout sharp variations in pressure. When the pressure in the bufferspace and/or buffer tank reaches a pre-set pressure threshold, a fuelcontrol valve could be opened and the internal combustion engine couldbe started to allow the engine to consume any excess vaporized LLH fuel.When the pressure in the buffer space and/or buffer tank reaches apre-set safe level, the internal combustion engine could be shut off andthe fuel control valve could be closed.

When the pressure in the buffer space and/or in the buffer tank reachesthe pre-set minimum level and the internal combustion engine mustcontinue to run, a heating system may be used to produce heat inside theLLH fuel tank. The heating system increases the evaporation rate of theLLH fuel and maintains the pressure in the fuel tank or in the buffertank to provide enough LLH fuel to the internal combustion engine. Thisis especially useful when the internal combustion engine must charge thebattery and/or provide additional power to an internal combustionengine.

The fifth challenge involves minimizing venting of greenhouse gases,especially vaporized LLH fuel into the atmosphere when the vehicle isidle. In the present invention, when the pressure in the fuel tank or inthe buffer tank reaches a pre-set pressure threshold, the internalcombustion engine could be started and a fuel control valve could beopened to allow the engine to consume any excess vaporized LLH fuel. Theinternal combustion engine coupled to a generator could be started toconsume excess fuel and to charge the battery when the pressure in thefuel tank or buffer tank reaches a pre-set threshold. The consumption ofexcess vaporized LLH fuel reduces the pressure in the buffer space or inthe buffer tank, eliminating the need to vent vaporized LLH fuel intothe atmosphere.

If the battery reaches a full charge and the vehicle is idle for a longperiod, then a digital control unit could turn on a bank of resistors todraw electrical power from the battery. Although this would result inthe emission of carbon oxides from fuel combustion, this has a muchlower greenhouse impact than venting excess vaporized LLH fuel (e.g.,methane) to the atmosphere. In addition, carbon dioxide does notrepresent a fire or explosion hazard while methane may ignite undercertain conditions. Similar to prior art systems, the vehicle would needto be parked in a well-ventilated area to avoid accumulation of carbonmonoxide, carbon dioxide or methane. As a last resort, the digitalcontrol unit could vent the excess vaporized LLH fuel to the atmospherethrough a safety valve.

The LLH fuel system and methods described herein allow for a simple fuelsystem and eliminate the need for complex heat exchangers, cryogenicpumps, regulator valves and other mechanisms to deliver liquid fuel tothe engine often seen in prior art. They also allow for a cheaper andlighter fuel tank design, and reduce the emissions of greenhouse gasesas compared to prior art systems.

These and other objects, features, and advantages will become apparentas reference is made to the following detailed description, preferredembodiments, and examples, given for the purpose of disclosure, andtaken in conjunction with the accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the presentinvention, reference should be made to the following detaileddisclosure, taken in conjunction with the accompanying drawings, inwhich like parts are given like reference numerals, and wherein:

FIG. 1 illustrates a schematic of a liquefied light hydrocarbon fuelsystem for a hybrid vehicle according to an embodiment of the presentinvention;

FIG. 2 illustrates a schematic of a liquefied light hydrocarbon fuelsystem for a hybrid vehicle according to an embodiment of the presentinvention;

FIG. 3A illustrates a schematic of an alternate fuel tank heater for theliquefied light hydrocarbon fuel system of FIG. 2;

FIG. 3B illustrates a cross-section of a fuel tank, chamber andinsulation for the liquefied light hydrocarbon fuel system of FIG. 3A;

FIG. 4 illustrates a schematic for an alternate dual fuel line for theliquefied light hydrocarbon fuel system of FIG. 1;

FIG. 5 illustrates a schematic for an alternate dual fuel tank for theliquefied light hydrocarbon fuel system of FIG. 2;

FIG. 6 illustrates a schematic for an alternate liquefied lighthydrocarbon fuel system for a stationary applications according to anembodiment of the present invention; and

FIG. 7 illustrates charts of power output of heating element, poweroutput of internal combustion engine (ICE)/generator, fuel tankpressure, power demand from electric motor and power drawn from batteryvs. time for Mode 1: low power requirements (e.g., start/stop vehicleoperation), Mode 2: high power requirements (e.g., acceleration, highspeeds, heavy loads or low-battery charge vehicle operation), and Mode3: no power requirements (e.g., idle or parked vehicle operation).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The following detailed description of various embodiments of the presentinvention references the accompanying drawings, which illustratespecific embodiments in which the invention can be practiced. While theillustrative embodiments of the invention have been described withparticularity, it will be understood that various other modificationswill be apparent to and can be readily made by those skilled in the artwithout departing from the spirit and scope of the invention.Accordingly, it is not intended that the scope of the claims appendedhereto be limited to the examples and descriptions set forth herein butrather that the claims be construed as encompassing all the features ofpatentable novelty which reside in the present invention, including allfeatures which would be treated as equivalents thereof by those skilledin the art to which the invention pertains. Therefore, the scope of thepresent invention is defined only by the appended claims, along with thefull scope of equivalents to which such claims are entitled.

Liquefied Light Hydrocarbon Fuel System

A liquefied light hydrocarbon fuel system 100 according to an embodimentof the present invention is illustrated in FIG. 1. The fuel system 100comprises a fuel tank 102, insulation 105 disposed around the fuel tank102, and a fuel line 108 connected to an inlet/outlet of the fuel tank102 and (through a fuel line 118) to an inlet of a fuel control valve120.

As shown in FIG. 1, the fuel tank 102 is connected through a fuel line108 to a re-fueling valve 110, a safety relief valve 112 and a pressuresensor 115. In an embodiment, the pressure sensor 115 is disposed withinthe fuel line 108. The pressure sensor 115 measures tank 102 pressures.In an embodiment, an inlet to the safety relief valve 112 connects tothe fuel line 108. In an embodiment, when the fuel tank 102 pressurereaches a pre-set upper threshold, the safety relief valve 112 may ventvaporized LLH fuel from the fuel tank 102 to atmosphere to prevent thetank pressure from exceeding the tank 102 design limits.

In an embodiment, the fuel line 108 serves as a LLH fuel intake torefill the tank 102. An outlet of the re-fueling valve 110 is connectedthrough the fuel line 108 to the fuel tank 102. The cold LLH fuelentering into the fuel tank 102, causes vaporized LLH fuel in the tank102 to condense and to reduce the tank 102 pressure, allowing refillingof the tank 102. In an embodiment, a level sensor (not shown) may bedisposed in the fuel tank 102 to prevent overfilling the tank 102. In anembodiment, the level sensor may be positioned to ensure a minimumbuffer space in the fuel tank 102.

In an embodiment, the fuel line 108 has a first end and a second end. Inan embodiment, the first end of the fuel line 108 extends into a bufferspace of the fuel tank 102.

In an embodiment, the fuel line 118 has a first end and a second end. Inan embodiment, the first end of the fuel line 118 connects to the secondend of the fuel line 108. In an embodiment, the second end of the fuelline 108 connects to an inlet of a shut-off valve 125 and an outlet ofthe shut-off valve 125 connects to the first end of the fuel line 118.During re-fueling, valve 125 is closed to prevent liquid fuel fromentering fuel line 118. In an embodiment, the second end of the fuelline 118 connects to the inlet of the fuel control valve 120. An outletof the fuel control valve 120 is adapted to connect to a fuel inlet of,for example, an internal combustion engine 122. In an embodiment, theinternal combustion engine 122 is a spark-plug engine. Although thecombustion engine 122 is discussed in this example, this embodimentwould also work with a sterling engine, a fuel cell or other similarenergy conversion devices, converting chemical energy in the fuel toelectrical energy and heat.

The fuel tank 102 is connected through fuel line 108 and throughshut-off valve 125 to the fuel line 118. The fuel line 118 is connectedto the inlet of the fuel control valve 120.

The fuel lines 108, 118 may be constructed of any suitable material. Forexample, the fuel lines 108, 118 may be constructed from the groupconsisting of aluminum, copper, steel alloy, stainless steel, rubber,braided rubber, nitrile rubber, silicon rubber and polyvinylchloride. Inan embodiment, the fuel lines 108, 118 are copper.

The fuel lines 108, 118 must also have a wall thickness sufficient tohandle the maximum tank 102 pressure. The fuel lines 108, 118 must havea cross-section to provide enough fuel to, for example, an internalcombustion engine 122. Although the combustion engine 122 is discussedin this example, this embodiment would also work with a sterling engine,a fuel cell or other similar energy conversion devices.

Under normal operating conditions, the fuel tank 102 must contain LLHfuel at a cryogenic temperature between about −170° C. and about −120°C. and at a pressure between about 15 psi and about 300 psi. The LLHfuel may be any suitable liquefied light hydrocarbons. For example, thelight hydrocarbons may be selected from the group consisting ofhydrogen, methane, natural gas, ethane, ethylene, propane, isopropane,propylene, propane gas, butane, isobutane, isobutene, butylene,petroleum gas and mixtures thereof. As ambient heat leaks into the fueltank 102 through insulation 105, the heat will cause the LLH fuel toboil and to evaporate, forming vaporized LLH fuel. In an embodiment, aLLH fuel (that is predominately methane) is typically stored at acryogenic temperature between about −170° C. and about −120° C. inside afuel tank at a pressure between about 15 psi and about 300 psi. In anembodiment, the LLH fuel is liquefied natural gas (LNG).

The fuel tank 102 may be constructed in any suitable shape and/orthickness for a vehicle application. For example, the shape of the fueltank 102 may be spherical, cylindrical with hemispherical ends, toroidalor any other shape suitable for relatively high pressures. Further, thefuel tank 102 must satisfy U.S. Department of Transportation (DOT)requirements. In an embodiment, the fuel tank 102 is a cylinder withhemispherical ends.

The fuel tank 102 may be constructed from any suitable material withresistance to cold temperatures and relatively high pressures. Forexample, the fuel tank 102 may be constructed from the group consistingof aluminum, copper, steel alloy and stainless steel. In an embodiment,the fuel tank 102 is steel alloy.

The fuel tank 102 is insulated to protect the LLH fuel from ambientheat. In other words, the LLH fuel must be maintained at a lowtemperature to minimize evaporation in the fuel tank 102. The insulation105 limits ambient heat from entering the fuel tank 102. The insulation105 may be any suitable material with low thermal conductivity. Forexample, the insulation 105 may be selected from the group consisting ofsupercritical-dried gels (e.g., Aerogel®, Spacetherm®), fiberglass,glass wool, wood, cardboard and polystyrene foam (e.g., Styrofoam®). Inan embodiment, the insulation consists of a plurality of layers ofsupercritical-dried gel blankets (e.g., Aerogel® blanket, Spacetherm®blanket) surrounded by an aluminum shell.

In an embodiment, the outer surface of the insulation 105 may be coveredwith a highly reflective material or radiation barrier (e.g., aluminumfoil) to reduce the amount of outside radiation entering the fuel tank102.

In another embodiment, the insulation 105 may be an air gap or a vacuumchamber in a double shell, Dewar-type fuel tank 102 to limit heatconduction and convection into the tank 102. In an embodiment, theoutside surface of the inner shell of the Dewar-type fuel tank 102 maybe covered with the highly reflective material or radiation barrier(e.g., aluminum foil), as discussed above.

The amount and type of insulation 105 should be optimized to keep theLLH evaporation rate below a desired level. This maximum evaporationrate (i.e., boiling rate) should allow the pressure in the fuel tank 102to be maintained below a safety limit to prevent overnight venting ofvaporized LLH fuel or running the internal combustion engine 122 morethan necessary to fully charge the battery 135 to consume excessvaporized LLH fuel.

In an embodiment, the fuel tank 102 has a tank heating system, asdepicted in FIGS. 1-3. In the embodiment of FIG. 1, the tank heatingsystem comprises a heating element 158 disposed adjacent to or withinthe fuel tank 102, and connected to a heating power control system 155.

In an embodiment, the heating element 158 may be disposed adjacent to anouter surface of the fuel tank 102, provided the fuel tank isconstructed of a thermally conductive material (e.g., copper, steelalloy, stainless steel). In an embodiment, the heating element 158 maybe disposed within the fuel tank 102.

The heating power control system 155 is connected through a DC powerline 152 to an electrical storage system (e.g., battery) 135. Theheating power control system 155 draws electrical energy from thebattery 135 through the DC power line 152 and controls the amount ofheat produced by the heating element 158 to vaporize LLH fuel and toincrease the fuel tank 102 pressure.

The heating power control system 155 may be any suitable control system.In an embodiment, the heating power control system 155 is an on/offrelay switch.

The heating element 158 may be any suitable heater for use with a LLHfuel tank. For example the heating element 158 may be selected from thegroup consisting of resistance heaters, cartridge heaters, band heatersand inductive heaters (if the fuel tank 102 is ferrous metal). In anembodiment, the heating element 158 is a cartridge heater. Typically, acartridge heater comprises an electric resistance embedded into astainless steel tube, wherein the electric resistance is isolated fromthe stainless steel tube with magnesium oxide or other similar compound.In an embodiment, the heating element 158 may be an inductive heater,provided the fuel tank 102 is constructed of a ferrous metal.

Alternatively, a heat transfer chamber 305 may be used instead of or inaddition to the heating element 158, as depicted in FIGS. 3A-3B.

In an embodiment, the fuel tank 102 has a buffer space for vaporized LLHfuel and to maintain the tank 102 pressure, as depicted in FIG. 1.Alternatively, a buffer tank 215 may be used in addition to the bufferspace, as depicted in FIG. 2. The buffer space in the LLH fuel tank 102and/or the buffer tank 215 must be sized to be large enough to permitvaporized LLH fuel to accumulate and to be drawn without sharpvariations in pressure.

As shown in FIG. 1, the fuel tank 102 is connected through fuel line 108to the fuel line 118. The fuel line 118 is connected to the inlet of thefuel control valve 120. The outlet of the fuel control valve 120 isadapted to connect to a fuel inlet of, for example, an internalcombustion engine 122 of a hybrid vehicle. Although the combustionengine 122 is discussed in this example, this embodiment would also workwith a sterling engine, a fuel cell or other similar energy conversiondevices.

During operation, the fuel control valve 120 regulates the flow ofvaporized LLH fuel into the fuel inlet of the internal combustion engine122. The internal combustion engine 122 converts calorific energy of thevaporized LLH fuel into kinetic energy.

For obvious reasons, the internal combustion engine 122 must be largeenough to meet the power requirements of the hybrid vehicle. Theinternal combustion engine 122 produces kinetic energy and drives agenerator shaft 128 in a generator 130. The generator shaft 128 rotatesand transmits kinetic energy from the internal combustion engine 122 tothe generator 130. The generator 130 converts the kinetic energy intoelectrical energy in the form of alternating current (AC). The generator130 may be any suitable electrical device capable of converting kineticenergy to electrical energy.

In an embodiment, the generator 130 is a permanent magnet two (2) orthree (3) phase synchronous electric machine.

In an embodiment, the generator 130 may include current and/or voltagesensors.

A battery charger system 132 comprises a rectifier, an inductance andother electronics to regulate current and voltage into an electricenergy storage system (e.g., battery) 135. The battery charger system132 rectifies the AC from the generator 130 into direct current (DC) andcontrols the rate of charge into the electrical energy storage system(e.g., battery) 135 to optimize battery 135 longevity.

The electrical energy storage system 135 may include a battery, acapacitor and other electric storage devices. In an embodiment, theelectrical energy storage system 135 is a battery. The battery 135 mustbe large enough to allow the internal combustion engine 122 to runperiodically overnight to consume excess vaporized LLH fuel withoutovercharging the battery 135.

An inverter 138 draws electrical energy from the battery 135 in the formof DC and coverts it into AC with a controllable frequency sufficient topower an electrical motor 140. The electrical motor 140 may be anysuitable asynchronous or synchronous motor that can be used to power avehicle drivetrain.

During regenerative braking, the electrical motor 140 acts as agenerator and the inverter 138 returns electrical energy to the battery135 in the form of DC. If the battery charge reaches a pre-set upperthreshold, then a digital control unit (DCU) 142 could draw electricalenergy from the battery into a resistor bank 145 or, as a last resort,vent vaporized LLH fuel to the atmosphere through the safety reliefvalve 112. The resistor bank 145 may be used to dissipate electricalenergy from the battery 135 to prevent overcharging when the vehicle isidle and the internal combustion engine 122 is run to consume excessvaporized LLH fuel and to reduce the fuel tank 102 pressure.

FIG. 1 illustrates a schematic diagram of a DCU 142 for the fuel system100 according to an embodiment of the present invention. The DCU 142comprises a computer specially programmed with adequate interfaces toreceive data signals from and send control signals to various componentsin, for example, a hybrid vehicle. For example, a software program maybe configured to optimize vehicle operation according to variouscriteria (e.g., energy efficiency, battery life, performance, emissionsreduction, total cost of ownership). It may also collect operating datathat can be used to further optimize the system.

The software program may also be configured by the user according to theuser's prioritized various criteria (e.g., energy efficiency, batterylife, performance, emission reduction, total cost of ownership). It mayalso allow user configurations and settings that can be used topersonalize the system

Referring to the drawings in general, and initially to FIG. 1 inparticular, an exemplary operating environment for implementingembodiments of the present invention is shown and designated generallyas a DCU 142. The DCU 142 is but one example of a suitable computingenvironment and is not intended to suggest any limitation as to thescope of use or functionality of the invention. Neither should the DCU142 be interpreted as having any dependency or requirement relating toany one or combination of the components illustrated.

Embodiments of the invention may be described in the general context ofcomputer code or machine-executable instructions stored as programmodules or objects and executable by one or more computing devices, suchas a laptop, server, mobile device, tablet, etc. Generally, programmodules including routines, programs, objects, components, datastructures, etc., refer to code that perform particular tasks orimplement particular abstract data types. Embodiments of the inventionmay be practiced in a variety of system configurations, includinghandheld devices, consumer electronics, general-purpose computers, morespecialty computing devices, and the like. Embodiments of the inventionmay also be practiced in distributed computing environments where tasksmay be performed by remote-processing devices that may be linked througha communications network.

With continued reference to FIG. 1, the DCU 142 includes a first signalbus 148 that directly or indirectly connects the following components:safety relief valve 112, pressure sensor 115, fuel control valve 120,generator 130, battery charger system 132, electrical energy storagesystem (e.g., battery) 135, inverter 138, electrical motor 140, resistorbank 145 controller and heating power control system 155.

The first signal bus 148 represents what may be one or more busses (suchas an address bus, data bus, or combination thereof). Although thevarious blocks of FIG. 1 are shown with lines for the sake of clarity,in reality, delineating various components is not so clear, andmetaphorically, the lines would more accurately be fuzzy. For example,one may consider a presentation component such as a display device to bean I/O component. Additionally, many processors have memory. Theinventors recognize that such is the nature of the art, and reiteratethat the diagram of FIG. 1 is merely illustrative of an exemplarydigital control unit that can be used in connection with one or moreembodiments of the present invention.

The DCU 142 may include a variety of computer-readable media.Computer-readable media can be any available media that can be accessedby the DCU 142 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer-readable media may comprise computer-storage mediaand communication media. The computer-storage media includes volatileand nonvolatile, removable and non-removable media implemented in anymethod or technology for storage of information such ascomputer-readable instructions, data structures, program modules orother data. Computer-storage media includes, but is not limited to,Random Access Memory (RAM), Read Only Memory (ROM), ElectronicallyErasable Programmable Read Only Memory (EEPROM), flash memory or othermemory technology, CD-ROM, digital versatile disks (DVD) or otherholographic memory, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium that canbe used to encode desired information and which can be accessed by theDCU 142.

The memory (not shown) may include computer-storage media in the form ofvolatile and/or nonvolatile memory. The memory may be removable,non-removable, or a combination thereof. Suitable hardware devicesinclude solid-state memory, hard drives, optical-disc drives, etc. TheDCU 142 includes a processor (not shown) that reads data from variousentities such as the memory or the I/O components discussed below.

The DCU 142 receives digital signals from the pressure sensor 115, thegenerator 130, the battery charger system 132, the electrical energystorage system (e.g., battery) 135, inverter 138 and the electricalmotor 140 through the first signal bus 148, as shown in FIG. 1.

The DCU 142 receives digital signals corresponding to the fuel tank 102pressure from the pressure sensor 115 and monitors the tank 102pressures through the first signal bus 148. When the fuel tank 102pressure reaches a pre-set upper threshold, the DCU 142 opens the fuelcontrol valve 120 and starts the internal combustion engine 122 to allowthe engine 122 to consume any excess vaporized LLH fuel and to reducethe tank 102 pressure. The internal combustion engine 122 drives thegenerator 130 that provides the electrical energy to charge the battery135 and drive the electric motor 140.

The DCU 142 receives digital or analog signals corresponding to currentand voltage from the generator 130 through the first signal bus 148.

The DCU 142 receives digital or analog signals corresponding to currentand voltage from the battery charger system 132 comprising therectifier, inductance and other electronics to regulate current andvoltage into the electrical energy storage system (e.g., battery) 135through the first signal bus 148.

The DCU 142 receives digital or analog signals corresponding to currentand voltage from the battery charger 132 and the electrical energystorage system (e.g., battery) 135 through the first signal bus 148.

The DCU 142 receives digital or analog signals corresponding to currentand voltage from the inverter 138 through the first signal bus 148.

The DCU 142 receives digital or analog signals corresponding to current,voltage and revolutions per minute (rpm) from the electrical motor 140through the first signal bus 148.

The DCU 142 also sends control signals through the first signal bus 148to the safety relief valve 112 (if electrically controllable), the fuelcontrol valve 120, the internal combustion engine 122, the batterycharger system 132, the inverter 138, the resistor bank 145 controllerand the heating power control system 155.

The DCU 142 sends control signals through the first signal bus 148 tothe battery charger system 132 to regulate current and voltage into theelectrical energy storage system (e.g., battery) 135.

The DCU 142 sends control signals through the first signal bus 148 tothe inverter 138 to control the speed and power of the electrical motor140.

The DCU 142 sends control signals through the first signal bus 148 to asolenoid to control the fuel control valve 120.

The DCU 142 sends control signals through the first signal bus 148 tothe resistor bank 145 controller to regulate the flow of electricalenergy into the bank 145.

The DCU 142 sends control signals through the first signal bus 148 tothe heating power control system 155 to regulate the flow of electricalenergy (by turning the power on and off) into the heating element 158.

The DCU 142 receives additional signals from a second signal bus 150,including driver commands for acceleration, braking, starting theengine, and the like.

Re-Fueling the Fuel Tank

Periodically, the hybrid vehicle may be re-fueled with LLH fuel througha re-fueling valve 110. Alternatively, a full LLH fuel tank 102 may beswapped for an empty one 102. An outlet of the re-fueling valve 110 isconnected through the fuel line 108 to the fuel tank 102. The cold LLHfuel entering into a cold fuel tank 102, causes vaporized LLH fuel inthe tank 102 to condense and to reduce the tank 102 pressure, allowingre-fueling of the tank 102.

In an embodiment, a level sensor may be disposed in the fuel tank 102 toprevent overfilling the tank 102. In an embodiment, the level sensor maybe positioned to ensure a minimum buffer space in the fuel tank 102.

Idle or Parked Vehicle Operation

During idle or parked vehicle operation, the hybrid vehicle may beconfigured to cycle the internal combustion engine 122 periodically toconsume excess vaporized LLH and to reduce pressure in the buffer spaceand/or the buffer tank 215. When the fuel control valve 120 is closed,pressure gradually accumulates in the buffer space and/or the buffertank 215 as ambient heat leaks into the fuel tank 102 through theinsulation 105 and vaporizes LLH fuel. See e.g., FIG. 7: Mode 3. Whenthe pressure increases to a pre-set upper threshold, the fuel controlvalve 120 is opened and the internal combustion engine 122 is started toconsume excess vaporized LLH fuel and to reduce the pressure of thebuffer space and/or the buffer tank 215. When the fuel control valve 120is opened, the vaporized LLH fuel flows out of the buffer space and/orthe buffer tank 215, and is consumed by the internal combustion engine122, reducing the pressure in the buffer space and/or the buffer tank215. Once the pressure drops to a pre-set safe level (consistent withthe minimum pressure required by the internal combustion engine 122),the fuel control valve 120 is closed and the engine 122 is stopped.During idle or parked operation, the internal combustion engine 122 maybe repeatedly cycled to consume excess vaporized LLH fuel and to reducepressure in the buffer space and/or the buffer tank 215.

While the internal combustion engine 122 is running, the engine 122produces kinetic energy and drives the generator shaft 128 in thegenerator 130, as discussed above. The generator 130 converts thekinetic energy into electrical energy in the form of AC. The batterycharger system 132 rectifies the AC from the generator 130 into DC andcontrols the rate of charge into the battery 135. If the battery 135charge reaches a pre-set upper threshold, the resistor bank 145 can beused to dissipate any excess electrical energy and to prevent thebattery 135 from overcharging.

Alternatively, the safety relief valve 112 may vent the vaporized LLHfuel to the atmosphere to reduce the pressure in the buffer space and/orthe buffer tank 215.

Normal Vehicle Operation

During normal operation, the hybrid vehicle may be configured to drawelectric power from the battery 135. The electrical motor 140 is poweredby the battery 135 through the inverter 138.

While the battery 135 charge remains above a pre-set lower threshold,the internal combustion engine 122 is started and stopped to consumeexcess vaporized LLH fuel and to reduce the fuel tank 102 pressure, asdiscussed above. See e.g., FIG. 7: Mode 3. The upper and lower fuel tank102 pressure limits are set such that the pressure range is adequate forthe proper function of the internal combustion engine 122.

When the battery 135 charge is discharged to a pre-set lower threshold,the internal combustion engine 122 is started to power the generator 130and begin recharging the battery 135. See e.g., FIG. 7: Mode 2. If thepressure in the fuel tank 102 drops below a pre-set lower threshold, theheating power control system 155 is started to provide heat to theheating element 158 in the tank 102, increasing evaporation of the LLHfuel in the tank 102, and increasing the pressure of the vaporized LLHfuel in the buffer space and/or buffer tank 215. Once the battery 135charge is recharged to a pre-set upper threshold, the fuel control valve120 is closed and the internal combustion engine 122 is stopped. Theinternal combustion engine 122 is cycled to consume excess vaporized LLHfuel and to reduce the fuel tank 102 pressure, as described above. Id.at Modes 2 & 3.

Sudden Acceleration, High Speeds and Heavy Loads Vehicle Operation

During sudden acceleration, high speeds and/or heavy loads operation,the hybrid vehicle may be configured to draw upon the battery 135 toprovide additional energy for the electrical motor 140, and, ifadditional power is required (e.g., battery charge is low), to heat thefuel tank 102 to provide additional vaporized LLH fuel for the internalcombustion engine 122. See e.g., FIG. 7: Mode 2. With the additionalvaporized LLH fuel from the tank 102, the engine 122 may be acceleratedor operated at high speeds or heavy loads without a sudden drop in LLHfuel flow or pressure. During sudden acceleration, high speed and/orheavy loads operation, the internal combustion engine 122 would haveenough vaporized LLH fuel to run properly.

Alternate Buffer System for Fuel Tank

An alternate buffer tank system 200 for the liquefied light hydrocarbonfuel system 100 according to an embodiment of the present invention isillustrated in FIG. 2. FIG. 2 shows the alternate buffer tank system 200for the fuel tank 102 that allows excess vaporized LLH fuel to leave thetank 102 and to be stored in a buffer tank 215.

In this embodiment, the buffer tank system comprises the buffer tank215, the safety relief valve 112 and the pressure sensor 115. Instead ofconnecting to the inlet of the fuel control valve 120, the second end ofthe fuel line 108 connects to an inlet to a buffer tank 215. Instead ofconnecting to the fuel control valve 120, an outlet to the buffer tank215 connects to an inlet to a solenoid valve 205, and an outlet to thesolenoid valve 205 connects to an inlet of a pressure regulator 210. Anoutlet of the pressure regulator 210 is adapted to connect to a fuelinlet of, for example, an internal combustion engine 122. In anembodiment, the internal combustion engine 122 is a spark-plug engine.Although the combustion engine 122 is discussed in this example, thisembodiment would also work with a sterling engine, a fuel cell or othersimilar energy conversion devices. Importantly, the fuel control valve120 and the solenoid valve 205 in connection with the pressure regulator210 serve the same functional purpose (i.e., to control the flow of thevaporized LLH fuel).

Similar to the fuel tank 102 of FIG. 1, the buffer tank 215 may beconstructed in any suitable shape and/or thickness for a vehicleapplication. For example, the shape of the buffer tank 215 may bespherical, cylindrical with hemispherical ends, toroidal or any othershape suitable for relatively high pressures. Further, the buffer tank215 must satisfy U.S. Department of Transportation (DOT) requirements.In an embodiment, the buffer tank 215 is cylindrical with hemisphericalends.

The buffer tank 215 may be constructed from any suitable material withresistance to cold temperatures and relatively high pressures. Forexample, the buffer tank 215 may be constructed from the groupconsisting of aluminum, copper, steel alloy and stainless steel. In anembodiment, the buffer tank 215 is steel alloy.

Similar to the embodiment of FIG. 1, the fuel tank 102 connects throughthe fuel line 108, the buffer tank 215, the solenoid valve 205 and thepressure regulator 210 to a fuel inlet of, for example, an internalcombustion engine 122. Although the combustion engine 122 is discussedin this example, this embodiment would also work with a sterling engine,a fuel cell or other similar energy conversion devices. As in FIG. 1,the fuel tank 102 is connected through a fuel line 108 to a re-fuelingvalve 110.

The DCU 142 receives digital signals corresponding to current, voltageand revolutions per minute (rpm) from the electrical motor controller225 through the first signal bus 148.

The DCU 142 sends control signals through the first signal bus 148 tothe resistor bank controller 220 to regulate the flow of electricalenergy into the bank 145.

Alternate Heating System for Fuel Tank

An alternate fuel tank heating system 300 for the liquefied lighthydrocarbon fuel system 100 according to an embodiment of the presentinvention is illustrated in FIGS. 3A-3B. FIG. 3A shows the alternateheating system 300 for the fuel tank 102 that allows incremental heat toenter the tank 102.

FIG. 3B shows a cross-section of a chamber 305, the fuel tank 102, andthe insulation 105 for the alternate fuel tank heating system 300 ofFIG. 3A. As shown in FIG. 3B, the chamber 305 is disposed between anouter surface of the fuel tank 102 and the insulation 105.

In an embodiment, the chamber 302 may be constructed from two (2) layersof metal separated by a gap to form an internal void. The edges of thetwo (2) layers are joined to form a sealed chamber. The edges may bejoined in any manner suitable to for a seal. To provide heat transferbetween the fuel tank 102 and the chamber 305, the outer surface of thefuel tank 102 is in contact with the inner metal layer of the chamber305. A heat transfer compound suitable for cryogenic temperatures may beused to improve the contact between the outer surface of the fuel tank102 and the inner metal layer of the chamber 305.

The chamber 305 may be constructed of any suitable metal. For example,the chamber 305 may be constructed from the group consisting ofaluminum, copper, steel alloy and stainless steel.

In another embodiment, the chamber 305 may be formed from a plasticshell disposed around the fuel tank 102. The plastic shell may be asingle molded piece or it may be a plurality of pieces. The plasticshell forms an interior void between the outer surface of the fuel tank102 and the inner surface of the plastic shell. The edges of the plasticshell are affixed to the fuel tank 102 to form a sealed chamber. Theedges of the plastic shell may be affixed to the fuel tank 102 in anymanner suitable to form a seal.

The plastic shell may be constructed from any suitable plastic. Forexample, the plastic shell may be constructed from the group consistingof polyvinylchloride (PVC) and any other plastics suitable for cryogenictemperatures.

In yet another embodiment, the chamber 305 may be formed from a gapbetween the outer surface of the fuel tank 102 and an inner surface ofthe insulation 105. A plurality of separators may be used to keep theinner surface of the insulation 105 from contacting the outer surface ofthe fuel tank 102. The inner surface of the insulation 105 may be sealedwith any suitable material to prevent leakage of a heat transfer fluidthrough the insulation 105. For example, the inner surface of theinsulation 105 may be sealed with a material selected from the groupconsisting of silicon, silicon rubber and any other sealing materialssuitable for cryogenic temperatures.

The chamber 305 is filled with a heat transfer fluid at a relatively lowpressure. The heat transfer fluid may be any suitable heating fluid. Forexample, the heat transfer fluid may be selected from the groupconsisting of air, nitrogen, helium or other inert gases with a boilingpoint below −163° C. In an embodiment, the heat transfer fluid isnitrogen.

The heat transfer fluid may be at any suitable pressure. For example,the heat transfer fluid may be at any pressure from about one (1)atmosphere to about three (3) atmospheres. In an embodiment, the heattransfer fluid is slightly above one (1) atmosphere.

In an embodiment, the heat transfer fluid line 310 has a first end and asecond end. The first end the heat transfer fluid line 310 connects anoutlet of the chamber 305 and the second end of the heat transfer fluidline 310 connects to an inlet of a butterfly valve 315.

The heat transfer fluid line 310 may be constructed from any suitablemetal or plastic. For example, the heat transfer fluid line 310 may beconstructed from the group consisting of copper and stainless steel,rubber, braided rubber, nitrile rubber, silicone rubber andpolyvinylchloride. In an embodiment, the line 310 is constructed fromrubber.

An outlet of the butterfly valve 315 connects to an inlet of a heattransfer coil 320 disposed within the heat exchanger 325; and an outletto the heat transfer fluid 320 connects to an inlet of the chamber 305.

The heat exchanger 325 may be constructed of any suitable metal orplastic. For example, the heat exchanger 325 may be constructed from thegroup consisting of aluminum, copper, steel alloy, stainless steel, tin,tin plate, polyvinylchloride and any other plastic suitable for therequired temperatures. In an embodiment, the heat exchanger 325 iscopper.

The heat transfer fluid coil 320 may be constructed of any suitablematerial. For example the heat transfer fluid coil 320 may beconstructed from the group consisting of copper, steel alloy andstainless steel. In an embodiment, the heat transfer fluid coil 320 iscopper.

The butterfly valve 315 controls the flow rate of the heat transferfluid from the outlet of the chamber 305 to the inlet of the chamber 305due to convectional heating. In an embodiment, the butterfly valve 315is in communication with and controlled by the digital control unit 142through a solenoid actuator or similar mechanism.

In an embodiment, ambient air flows across the outer surface of the heattransfer fluid coil 320 to heat the coil 320. In this embodiment, theheat exchanger 325 is not required.

When required, the heat exchanger 325 has an inlet and an outlet forheat exchanger fluid. In an embodiment, the inlet to the heat exchanger325 is adjacent to the outlet of the heat transfer fluid coil 320; andoutlet to the heat exchanger 325 is adjacent to the inlet of the coil320. In an embodiment, the inlet to the heat exchanger 325 is adjacentto the inlet of the heat transfer fluid coil 320; and outlet to the heatexchanger 325 is adjacent to the outlet of the coil 320.

The heat exchanger fluid may be any suitable heating/cooling fluid. Forexample, the heat exchanger fluid may be selected from the groupconsisting of air, nitrogen, carbon dioxide, water and treated water. Inan embodiment, the heat exchanger fluid is treated water. As typical inautomotive applications, the engine cooling water may be treated withcorrosion inhibitors and/or antifreeze additives.

In an embodiment, an outlet of a water cooling system (e.g., outlet toradiator) for the internal combustion engine 122 may be connected to theinlet of the heat exchanger 325. The treated water flows across theouter surface of the heat transfer fluid coil 320 to heat the coil 320.An outlet of the heat exchanger 325 is connected to an inlet of thewater cooling system (e.g., inlet to radiator).

Similar to the embodiment of FIG. 2, a fuel line 108 connects the fueltank 102 to a buffer tank 215.

Alternate Dual Fuel Line System

An alternate dual fuel line system 400 for the liquefied lighthydrocarbon fuel system 100 according to an embodiment of the presentinvention is illustrated in FIG. 4. FIG. 4 shows the alternate dual fuelline system 400 that reduces the net heat accumulation in the fuel tank102.

As shown in FIG. 4, the fuel tank 102 is connected through a first fuelline 415 and a first solenoid valve 420 to the buffer tank 215. An inletto the safety relief valve 112 is connected to the fuel tank 102.

In an embodiment, the first fuel line 415 has a first end and a secondend. In an embodiment, the first end of the first fuel line 415 extendsinto a buffer space of the fuel tank 102. In an embodiment, a fuel coil410 has a first end and a second end. The first end of the first fuelline 415 connects to the first end of the fuel coil 410, and second endof the fuel coil 410 connects to an outlet of an orifice plate 405. Thesecond end of the first fuel line 415 connects to an inlet of the firstsolenoid valve 420.

The fuel coil 410 may be constructed of any suitable material with ahigh thermal conductivity. For example, the fuel coil 410 may beconstructed from the group consisting of aluminum, copper, steel alloyand stainless steel. In an embodiment, the fuel coil 410 is copper.

The fuel line 415 may be constructed of any suitable material. Forexample, the fuel line 415 may be constructed from the group consistingof aluminum, copper, steel alloy, stainless steel, rubber, braidedrubber, nitrile rubber, silicon rubber and polyvinylchloride. In anembodiment, the fuel line 415 is copper.

The fuel line 415 must have a wall thickness sufficient to handle themaximum fuel tank 102 pressure. The fuel line 415 must have across-section to provide enough fuel to, for example, an internalcombustion engine 122. Although the combustion engine 122 is discussedin this example, this embodiment would also work with a sterling engine,a fuel cell or other similar energy conversion devices.

The orifice plate 405 limits the flow of LLH fuel, acting as athrottling mechanism.

The fuel tank 102 is also connected through a second fuel line 425 and asecond solenoid valve 430 to the buffer tank 215.

In an embodiment, the second fuel line 425 serves as a LLH fuel intaketo refill the fuel tank 102. An outlet of the re-fueling valve (notshown) is connected through the second fuel line 425 to the fuel tank102. In an embodiment, a level sensor (not shown) may be disposed in thefuel tank 102 to prevent overfilling the tank 102. In an embodiment, thelevel sensor may be positioned to ensure a minimum buffer space in thefuel tank 102.

In an embodiment, the second fuel line 425 has a first end and a secondend. In an embodiment, the first end of the second fuel line 425 extendsinto a buffer space of the fuel tank 102.

The second fuel line 425 may be constructed of any suitable material.For example, the second fuel line 425 may be constructed from the groupconsisting of copper, steel alloy, stainless steel, rubber, braidedrubber, nitrile rubber, silicon rubber and polyvinylchloride. In anembodiment, the fuel line 425 is copper.

The second fuel line 425 must have a wall thickness sufficient to handlethe maximum fuel tank 102 pressure. The second fuel line 425 must have across-section to provide enough fuel to, for example, an internalcombustion engine 122. Although the combustion engine 122 is discussedin this example, this embodiment would also work with a sterling engine,a fuel cell or other similar energy conversion devices.

The second end of the first fuel line 415 connected to an inlet of afirst solenoid valve 420 to the buffer tank 215.

Similar to the embodiment of FIG. 1, the digital control unit 142controls the first solenoid valve 420 and the second solenoid valve 430.Typically, the first solenoid valve 420 and the second solenoid valve430 would not open at the same time.

When the first solenoid valve 420 is open and vaporized LLH fuel flowsthrough the first fuel line 415 to the buffer tank 215, the orificeplate 405 creates a pressure differential between the fuel tank 102 andinside the fuel coil 410. As the vaporized LLH fuel flows through theorifice plate 405 and expands into the fuel coil 410, the temperaturedrops due to the Joule-Thompson effect. This reduces the temperature forthe fuel coil 410 below the temperature of the buffer space inside fueltank 102 and results in heat transfer from the tank 102 to the vaporizedLLH fuel inside the coil 410. This heat is removed by the vaporized LLHfuel flowing through fuel line 415 to the buffer tank 215.

The first fuel line may be used during idle or low power demand periodsto cool the fuel tank 102 and to reduce the tank 102 pressure.

The second end of the second fuel line 425 connects to an inlet of thesecond solenoid valve 430 to the buffer tank 215. Similar to theembodiments of FIGS. 1-2, the second fuel line 425 is used during normaloperation.

An outlet to the buffer tank 215 connects to the inlet to the pressureregulator 210. The outlet of the pressure regulator 210 is adapted toconnect to a fuel inlet of, for example, an internal combustion engine122. Although the combustion engine 122 is discussed in this example,this embodiment would also work with a sterling engine, a fuel cell orother similar energy conversion devices.

Alternate Dual Fuel Tank System

An alternate dual fuel tank system 500 for the liquefied lighthydrocarbon fuel system 100 according to an embodiment of the presentinvention is illustrated in FIG. 5. FIG. 5 shows the alternate dual fueltank system 500 that provides additional vapor fuel to leave a secondfuel tank 505 and to be stored in the buffer tank 215.

As shown in FIG. 5, the second fuel tank 505 is connected through athird fuel line 510 and a third solenoid valve 515 to the buffer tank215.

In an embodiment, the third fuel line 510 has a first end and a secondend. In an embodiment, the first end of the third fuel line 510 extendsinto a buffer space of the second fuel tank 505.

The third fuel line 510 may be constructed of any suitable material. Forexample, the third fuel line 510 may be constructed from the groupconsisting of copper, steel alloy, stainless steel, rubber, braidedrubber, nitrile rubber, silicon rubber and polyvinylchloride. In anembodiment, the third fuel line 510 is copper.

The third fuel line 510 must have a wall thickness sufficient to handlethe maximum fuel tank 505 pressure. The third fuel line 510 must have across-section to provide enough fuel to, for example, an internalcombustion engine 122. Although the combustion engine 122 is discussedin this example, this embodiment would also work with a sterling engine,a fuel cell or other similar energy conversion devices.

The second fuel tank 505 may be constructed in any suitable shape and/orthickness for a vehicle application. For example, the shape of thesecond fuel tank 505 may be spherical, cylindrical with hemisphericalends, toroidal or any other shape suitable for relatively highpressures. Further, the second fuel tank 505 must satisfy U.S.Department of Transportation (DOT) requirements. In an embodiment, thesecond fuel tank 505 is a cylinder with hemispherical ends.

The second fuel tank 505 may be constructed from any suitable materialwith resistance to relatively high pressures and, in an alternativeembodiment, to cold temperatures. For example, the second fuel tank 505may be constructed from the group consisting of aluminum, copper, steelalloy and stainless steel. In an embodiment, the second fuel tank 505 issteel alloy.

In an embodiment, the second fuel tank 505 is not insulated because thetank 505 is maintained at ambient temperatures.

Under normal ambient operating conditions, the second fuel tank 505 mustcontain a hydrocarbon fuel that can be liquefied at ambient temperaturesand at a pressure between about 15 psi and about 300 psi (e.g., LPG).For example, light hydrocarbons may be selected from the groupconsisting of propane, isopropane, propylene, propane gas, butane,isobutane, isobutene, butylene, petroleum gas and mixtures thereof. Inan embodiment, the hydrocarbon fuel in the second fuel tank 505 is LPG.

In an alternate embodiment, the second fuel tank 505 is insulatedbecause the tank is maintained at cryogenic temperatures.

Under normal cryogenic operating conditions, the second fuel tank 505must contain LLH fuel at a cryogenic temperature between about −170° C.and about −120° C. and at a pressure between about 15 psi and about 300psi. Similar to the embodiments of FIGS. 1-4, the LLH fuel may be anysuitable liquefied light hydrocarbons. For example, the lighthydrocarbons may be selected from the group consisting of hydrogen,methane, natural gas, ethane, ethylene, propane, isopropane, propylene,propane gas, butane, isobutane, isobutene, butylene, petroleum gas andmixtures thereof. As heat leaks into the second fuel tank 505 throughthe insulation (not shown), the heat will cause the LLH fuel to boil andto evaporate, forming vaporized LLH fuel. In an embodiment, a LLH fuel(that is predominately methane) is typically stored at a cryogenictemperature between about −170° C. and about −120° C. inside a fuel tankat a pressure between about 15 psi and about 200 psi. In an embodiment,the LLH fuel in the second fuel tank 505 is LNG.

The second fuel tank 505 is insulated to protect the LLH fuel fromambient heat. In other words, the LLH fuel must be maintained at a lowtemperature to minimize evaporation in the second fuel tank 505. Theinsulation limits ambient heat from entering the second fuel tank 505.The insulation may be any suitable material with low thermalconductivity. For example, the insulation may be selected from the groupconsisting of supercritical-dried gels (e.g., Aerogel®, Spacetherm®),fiberglass, glass wool, wood, cardboard and polystyrene foam (e.g.,Styrofoam®). In an embodiment, the insulation consists of a plurality oflayers of supercritical-dried gel blankets (e.g., Aerogel® blanket,Spacetherm® blanket) surrounded by an aluminum shell.

In an embodiment, the outer surface of the insulation may be coveredwith a highly reflective material or radiation barrier (e.g., aluminumfoil) to reduce the amount of outside radiation entering the second fueltank 505.

In another embodiment, the insulation may be an air gap or a vacuumchamber in a double shell, Dewar-type second fuel tank 505 to limit heatconduction and convection into the second tank 505. In an embodiment,the outside surface of the inner shell of the Dewar-type second fueltank 505 may be covered with the highly reflective material or radiationbarrier (e.g., aluminum foil), as discussed above.

The amount and type of insulation should be optimized to keep the LLHevaporation rate below a desired level. This maximum evaporation rate(i.e., boiling rate) should allow the pressure in the second fuel tank505 to be maintained below a safety limit to prevent overnight ventingof vaporized LLH fuel or running the internal combustion engine 122 toconsume excess vaporized LLH fuel levels.

In an embodiment, the second fuel tank 505 has a tank heating system, asdepicted in FIGS. 1-3. In an embodiment, the tank heating systemcomprises a second heating element (not shown) disposed adjacent to orwithin the second fuel tank 505 and connected to a second heating powercontrol system (not shown).

In an embodiment, the second heating element (not shown) may be disposedadjacent to an outer surface of the second fuel tank 505, provided thefuel tank is constructed of a thermally conductive material (e.g.,copper, steel alloy, stainless steel). In an embodiment, the secondheating element may be disposed within the second fuel tank 505.

The second heating power control system (not shown) is connected througha second DC power line (not shown) to a battery 135. The second heatingpower control system draws electrical energy from the battery 135through a second DC power line and controls the amount of heat producedby the second heating element to vaporize LLH fuel and to maintain thesecond tank 505 pressure.

The second heating element may be any suitable heater for use with a LLHfuel tank. For example the second heating element may be selected fromthe group consisting of inductive heaters, resistance heaters, cartridgeheaters, band heaters and induction heaters (if the fuel tank 505 isferrous metal). In an embodiment, the second heating element is acartridge heater. In an embodiment, the second heating element may be aninductive heater, provided the second fuel tank 505 is constructed of aferrous metal.

Alternatively, a second heat transfer chamber (not shown) may be usedinstead of the second heating element, as depicted in FIGS. 3A-3B.

In an embodiment, the second fuel tank 505 has a buffer space forvaporized LLH fuel and to maintain the second tank 505 pressure.Alternatively, a buffer tank 215 may be used in addition to or insteadof the buffer space, as depicted in FIG. 5.

Similar to the embodiment of FIG. 4, the second fuel tank 505 isconnected through the third fuel line 510, the third solenoid valve 515,the buffer tank 215 and the pressure regulator 210 to a fuel inlet of,for example, an internal combustion engine 122. Although the combustionengine 122 is discussed in this example, this embodiment would also workwith a sterling engine, a fuel cell or other similar energy conversiondevices. The second end of the third fuel line 510 is connected to aninlet of the third solenoid valve 515, and an outlet of the thirdsolenoid valve 515 is connected to an inlet of the buffer tank 215. Ifthe first fuel tank 102 cannot vaporize enough LLH fuel to meet demands,or if the first tank 102 runs out of fuel, the third solenoid valve 515can be opened for the second tank 505 to provide additional fuel asbackup.

Similar to the embodiments of FIGS. 1 and 4, the DCU 142 controls thethird solenoid valve 515.

The outlet to the buffer tank 215 connects to the inlet to the pressureregulator 210. The outlet of the pressure regulator 210 is adapted toconnect to a fuel inlet of, for example, an internal combustion engine122. Although the combustion engine 122 is discussed in this example,this embodiment would also work with a sterling engine, a fuel cell orother similar energy conversion devices.

In an embodiment, the third fuel line 510 may serve as a LLH fuel intaketo refill the second fuel tank 505. An outlet of the re-fueling valve(not shown) is connected through the third fuel line 510 to the secondfuel tank 505. In an embodiment, a level sensor (not shown) may bedisposed in the second fuel tank 505 to prevent overfilling the secondtank 505. In an embodiment, the level sensor may be positioned to ensurea minimum buffer space in the second fuel tank 505.

Alternate Energy Storage System

An alternate energy storage system 600 for the liquefied lighthydrocarbon fuel system 100 according to an embodiment of the presentinvention is illustrated in FIG. 6. FIG. 6 shows the alternate energystorage system 600 that provides energy to a machine, a vehicle, a houseor a commercial/industrial facility. This embodiment can be usefulespecially in emerging markets, where fuel oil and/or diesel are used toproduce heat and electricity in remote locations.

In this embodiment, the internal combustion engine 122, for example,stores thermal energy (heat) in a hot water heater system 605. Althoughthe combustion engine 122 is discussed in this example, this embodimentwould also work with a sterling engine, a fuel cell or other similarenergy conversion devices. The hot water heater system 605 comprises awater tank 610, a first water line 615, a heating coil 620 and a secondwater line 625. The heating coil 620 is disposed within the water tank610.

The first water line 615 has a first end and a second end, the heatingcoil 620 has a first end and a second end, and the second water line 625has a first end and a second end. The first end of the first water line615 connects to an outlet of the cooling system to the internalcombustion engine 122, and the second end of the first water line 625connects to the first end of the heating coil 620. The second end of theheating coil 620 connects to the first end of the second water line 625,and the second end of the second water line 625 connects to an inlet tothe cooling system of the internal combustion engine 122.

The first water line 615 and the second water line 625 may beconstructed of any suitable material. For example, the water lines 615,625 may be constructed from the group consisting of copper, steel alloyand stainless steel, rubber, polyvinylchloride and any other plasticthat is suitable for handling cooling system water from an internalcombustion engine. In an embodiment, the water lines 615, 625 arecopper.

The heating coil 620 may be constructed of any suitable material with ahigh thermal conductivity. For example, the heating coil 620 may beconstructed from the group consisting of copper, steel alloy andstainless steel. In an embodiment, the heating coil 620 is copper.

In an embodiment, electrical energy from an inverter 630 may be used topower electrical devices 635 or, if necessary, transfer electricalenergy to a main electrical grid 640. In an embodiment, the inverter 630comprises an interface to provide electrical energy to electricaldevices 635 and/or transfer electrical energy to the power grid 640.This embodiment may be used to provide heat and/or electric power tomachines, vehicles (e.g., vessels, trains, busses, and motor homes), ahouse or a commercial/industrial facility.

The embodiments and examples set forth herein are presented to bestexplain the present invention and its practical application and tothereby enable those skilled in the art to make and utilize theinvention. However, those skilled in the art will recognize that theforegoing description and examples have been presented for the purposeof illustration and example only. The description as set forth is notintended to be exhaustive or to limit the invention to the precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching without departing from the spirit and scope of thefollowing claims.

DEFINITIONS

As used herein, the terms “a,” “an,” “the,” and “said” when used inconjunction with the term “comprising” means one or more, unless thecontext dictates otherwise.

As used herein, the term “about” means the stated value plus or minus amargin of error or plus or minus 10% if no method of measurement isindicated.

As used herein, the term “or” means “and/or” unless explicitly indicatedto refer to alternatives only or if the alternatives are mutuallyexclusive.

As used herein, the terms “comprising,” “comprises,” and “comprise” areopen-ended transition terms used to transition from a subject recitedbefore the term to one or more elements recited after the term, wherethe element or elements listed after the transition term are notnecessarily the only elements that make up the subject.

As used herein, the terms “containing,” “contains,” and “contain” havethe same open-ended meaning as “comprising,” “comprises,” and“comprise,” provided above.

As used herein, the terms “having,” “has,” and “have” have the sameopen-ended meaning as “comprising,” “comprises,” and “comprise,”provided above.

As used herein, the terms “including,” “includes,” and “include” havethe same open-ended meaning as “comprising,” “comprises,” and“comprise,” provided above.

As used herein, the phrase “consisting of” is a closed transition termused to transition from a subject recited before the term to one or morematerial elements recited after the term, where the material element orelements listed after the transition term are the only material elementsthat make up the subject.

As used herein, the phrase “consisting essentially of” occupies a middleground, allowing the addition of non-material elements that do notsubstantially change the nature of the invention, such as variousbuffers, differing salts, extra wash or precipitation steps, pHmodifiers, and the like.

As used herein, the term “simultaneously” means occurring at the sametime or about the same time, including concurrently.

INCORPORATION BY REFERENCE

All patents and patent applications, articles, reports, and otherdocuments cited herein are fully incorporated by reference to the extentthey are not inconsistent with this invention.

What is claimed is:
 1. A liquefied light hydrocarbon fuel system for ahybrid vehicle, comprising: a) a fuel tank having a buffer spaceconfigured to provide room for vaporized light hydrocarbon fuel; b)insulation, wherein the insulation is disposed around the fuel tank; c)a first fuel line having a first end and a second end, wherein the firstend of the first fuel line extends into the buffer space of the fueltank; d) a pressure sensor measuring pressure in the fuel tank andsending digital signals corresponding to pressure to a digital controlunit through a first signal bus, wherein the pressure sensor is disposedwithin the first fuel line; e) a safety relief valve, wherein an inletto the safety relief valve connects to the first fuel line through ashut-off valve; f) a second fuel line having a first end and a secondend, wherein the first end of the second fuel line connects to thesecond end of the first fuel line through the shut-off valve; g) a fuelcontrol valve, wherein an inlet of the fuel control valve connects tothe second end of the second fuel line and wherein an outlet of the fuelcontrol valve is adapted to connect to a fuel inlet of an internalcombustion engine of the-hybrid vehicle whereby the fuel control valveis configured to regulate the flow of vaporized fuel into the internalcombustion engine; and h) a tank heating system, further comprising: i.a heating element, wherein the heating element is disposed adjacent toor within the fuel tank whereby the heating element produces heat tovaporize liquefied light hydrocarbon fuel and increase the fuel tankpressure; ii. a heating power control system connected to the heatingelement and connected through a direct current power line to anelectrical energy storage system of the hybrid vehicle whereby theheating power control system draws electrical energy from the electricalenergy storage system through the direct current power line and controlsthe amount of heat produced by the heating element.
 2. The fuel systemof claim 1, wherein the liquefied light hydrocarbon fuel is selectedfrom the group consisting of methane, ethane, ethylene, propane,propylene, butane, isobutane, butylene and mixtures thereof.
 3. The fuelsystem of claim 1, wherein the fuel control valve further comprises asolenoid valve and a pressure regulator, wherein an outlet of thesolenoid valve connects to an inlet of the pressure regulator andwherein an outlet of the pressure regulator is adapted to connect to thefuel inlet of the internal combustion engine.
 4. The fuel system ofclaim 1, wherein the second fuel line further comprises a buffer tank,wherein the second end of the second fuel line connects to an inlet ofthe buffer tank and wherein an outlet of the buffer tank is connectedthrough the first fuel line to the first fuel tank.
 5. The fuel systemof claim 4, wherein the inlet of the safety relief valve connects to thebuffer tank and wherein the pressure sensor is disposed within thebuffer tank.
 6. The fuel system of claim 1, wherein the tank heatingsystem further comprises: a) a chamber disposed between an outer surfaceof the fuel tank and the insulation, wherein the chamber is filled witha heat transfer fluid at a pressure between about 1 atmosphere and about3 atmospheres; b) a heat transfer line having a first end and a secondend, wherein the first end of the heat transfer line connects an outletof the chamber; c) a butterfly valve, wherein the second end of the heattransfer line connects to an inlet of the butterfly valve; and d) a heattransfer coil having a first end and a second end, wherein the heattransfer coil is disposed within a heat exchanger and wherein an outletof the butterfly valve connects to an inlet of the heat transfer coiland an outlet to the heat transfer coil connects to an inlet of thechamber.
 7. The fuel system of claim 6, wherein the heat transfer fluidis selected from the group consisting of air, nitrogen, and helium. 8.The fuel system of claim 7, wherein an outlet of a water cooling systemfor the internal combustion engine connects to an inlet of the heatexchanger and wherein an outlet of the heat exchanger connects to aninlet of the water cooling system of the internal combustion engine. 9.The fuel system of claim 6, further comprising: a) a third fuel linehaving a first end and a second end; b) a fuel coil having a first endand a second end, wherein the first end of the third fuel line connectsto the first end of the fuel coil and second end of the fuel coilconnects to an outlet of an orifice plate; c) a solenoid valve, whereinthe second end of the third fuel line connects to an inlet of thesolenoid valve and wherein the outlet of the solenoid valve connects toa buffer tank.
 10. The fuel system of claim 8, further comprising: a) asecond fuel tank having a buffer space; b) a third fuel line having afirst end and a second end, wherein the first end of the third fuel lineextends into a buffer space of the second fuel tank; c) a solenoidvalve, wherein an inlet of the solenoid valve connects to the second endof the third fuel line and wherein an outlet of the solenoid valve isadapted to connect to the fuel inlet to the internal combustion engine.11. The fuel system of claim 10, further comprising a second insulation,wherein the second insulation is disposed around the second fuel tank.12. The fuel system of claim 10, wherein the light liquefied hydrocarbonfuel is selected from the group consisting of propane, isopropane,propylene, butane, isobutane, butylene and mixtures thereof.
 13. Thefuel system of claim 1, further comprising: a. a generator having agenerator shaft mechanically connected to a crankshaft of the internalcombustion engine, wherein the generator shaft rotates and transmitskinetic energy from the internal combustion engine to the generator andwherein the generator converts the kinetic energy into electrical energyin the form of alternating current; b. a battery charger systemconnected to an output of the generator, wherein the battery chargersystem rectifies the alternating current from the generator into directcurrent and controls the rate of charge into an input of the electricalenergy storage system; c. an inverter connected to an output of theelectrical energy storage system, wherein the inverter draws electricalenergy from the electrical energy storage system in the form of directcurrent and converts the direct current from the electrical energystorage system into alternating current; d. an electrical motor orelectrical load connected to an output of the inverter, wherein theelectrical motor or electrical load is powered by the alternatingcurrent from the inverter; and e. a resistor bank connected to theoutput of the electrical-energy storage system, wherein the resistorbank dissipates excess electrical energy from the electrical energystorage system.
 14. The fuel system of claim 13, wherein the digitalcontrol unit is configured to: a. send a first set of control signalsthrough the first signal bus to the battery charger system 132 toregulate current and voltage into the electrical energy storage system135; b. send a second set of control signals through the first signalbus to the inverter to control the speed and power of the electricalmotor; c. send a third set of control signals through the first signalbus to a solenoid to control the fuel control valve; d. send a fourthset of control signals through the first signal bus to the resistor bankto regulate the flow of electrical energy into the resistor bank; e.send a fifth set of control signals through the first signal bus to theheating power control system to regulate the flow of electrical energyinto the heating element; f. receive a sixth set of signals from asecond signal bus, including driver commands for acceleration, brakingand starting the engine.
 15. A method of using the fuel system of claim13, comprising the steps of: a) providing the fuel system of claim 13;b) setting an upper pressure threshold for the buffer space in the fueltank; c) monitoring the pressure in the buffer space of the fuel tankwith the pressure sensor; and d) when the upper pressure threshold isachieved, opening the fuel control valve and starting the internalcombustion engine to consume excess vaporized liquefied lighthydrocarbon fuel and to reduce pressure in the buffer space of the fueltank.
 16. The method of claim 15, further comprising the steps of: a)setting a lower pressure threshold for the buffer space in the fueltank; b) monitoring the pressure in the buffer space of the fuel tank;and c) when the lower pressure threshold is achieved, closing the fuelcontrol valve and stopping the internal combustion engine.
 17. Themethod of claim 15, further comprising the steps of: a) setting an uppercharge threshold for a battery; b) monitoring the charge of the battery;and c) when the upper charge threshold is achieved, dissipating anyexcess electrical energy into the resistor bank.
 18. The method of claim15, further comprising the steps of: a) setting a lower charge thresholdfor a battery; b) monitoring the charge of the battery; and c) when thelower charge threshold is achieved, opening the fuel control valve andstarting the internal combustion engine to recharge the battery.
 19. Themethod of claim 15, further comprising the steps of: a) heating the fueltank to provide additional vaporized liquefied light hydrocarbon fuelfor the internal combustion engine; and b) opening the fuel controlvalve and starting the internal combustion engine to consume thevaporized liquefied light hydrocarbon fuel.
 20. The fuel system of claim1, further comprising: a) a third fuel line having a first end and asecond end; b) a fuel coil having a first end and a second end, whereinthe first end of the third fuel line connects to the first end of thefuel coil and second end of the fuel coil connects to an outlet of anorifice plate; c) a solenoid valve, wherein the second end of the thirdfuel line connects to an inlet of the solenoid valve and wherein theoutlet of the solenoid valve connects to the second fuel line.
 21. Thefuel system of claim 13 wherein the digital control unit furthercomprises a. a processor configured with adequate interfaces to receivepredetermined data signals from the hybrid vehicle comprising: i. afirst set of signals corresponding to the fuel tank pressure from thepressure sensor; ii. a second set of signals corresponding to currentand voltage from the generator; iii. a third set of signalscorresponding to current and voltage from the battery charger system toregulate current and voltage into the electrical energy storage systemiv. a fourth set of signals corresponding to current and voltage fromthe inverter; v. a fifth set of signals corresponding to current,voltage and revolutions per minute from the electrical motor; b. machineinstructions loaded into the processor configured to control theoperation of the hybrid vehicle; whereby the processor reads the datasignals from the hybrid vehicle, and using the machine instructions,sends control signals, through the first signal bus to control thehybrid vehicle.
 22. The fuel system of claim 1 whereby the electricalenergy storage system comprises a battery or a capacitor.
 23. The fuelsystem of claim 1 wherein the heating power control system comprisesrelay switch.